Serum troponin T, a myocardial contractile protein, has been reported to be a sensitive marker for the diagnosis of acute myocardial infarction. However, there have been few reports on its ability to detect coronary reperfusion and to predict left ventricular function in the chronic stage. Twenty two patients (20 males and 2 females, 61 +/- 10 y.o.) with acute myocardial infarction were enrolled in this study. They were divided into 2 groups, one with successful reperfusion (group A: n = 13) and one without reperfusion (Group B: n = 9) and the serial changes of their serum troponin T levels were evaluated. Serum myosin light chain was measured in another group of patients with acute myocardial infarction without history of old myocardial infarction (group C: n = 8). The slope of the logarithm of serum troponin T on a time-value curve was calculated from the time of admission to the first peak within 24 hours of the onset of acute myocardial infarction. The correlation coefficient between the late peak of serum troponin T and the left ventricular ejection fraction in 11 patients with first Q wave acute myocardial infarction was compared with that between the serum myosin light chain peak and the left ventricular ejection fraction in group C. 1) The slope of the logarithm of serum troponin T on the time-value curve in group A was greater than that in group B (0.57 +/- 0.45 vs. 0.22 +/- 0.16) (p < 0.05). 2) There was a good correlation between the late peak level of serum troponin T (78 +/- 10 hours after the onset) and the left ventricular ejection fraction in 11 patients with first Q wave acute myocardial infarction (r = -0.84, p < 0.01), which was similar to that of the serum myosin light chain peak and the left ventricular ejection fraction (r = -0.72, p < 0.05). On the other hand, there was no correlation between the peak level of serum creatine phosphokinase and the left ventricular ejection fraction (r = -0.55, NS). The serum troponin T levels 24, 36, 48 and 60 hours after the onset also correlated well with the left ventricular ejection fraction (r = -0.65, -0.7, -0.65 and -0.89, respectively). We conclude that the serial measurement of serum troponin T in patients with acute myocardial infarction is useful in the evaluation of left ventricular function in the chronic stage and that it is a potential non-invasive predictor of coronary reperfusion.